Regression-based gain optimization for alpha imaging detectors in spectroscopic alpha autoradiography

Preclinical studies on targeted alpha therapy leverage stereoscopic alpha autoradiography to distinguish alpha-emitting isotopes based on their energy or half-life characteristics and to visualize their spatial distributions. An alpha imaging detector adopted a monolithic scintillation detector for energy-based isotope discrimination. However, when estimating the deposited energy as the sum of multi-channel photosensor signals, the detector response may vary with the interaction position owing to geometric asymmetry and inter-channel electronic variations. Such nonuniformity degrades the energy estimation accuracy and resolution. Although a regression-based gain optimization (RGO) method has been developed to address this issue, the application on alpha detectors introduced new technical challenges. Therefore, in this study, the RGO method was modified and applied to an alpha imaging detector to verify its effectiveness, considering the characteristics of alpha particles and the imaging system. The proposed procedure was experimentally validated using an 241 Am source and an 225 Ac-labeled radiopharmaceutical. The results demonstrated improved energy uniformity across the detector area, with the energy resolution for 8.4 MeV alpha particles from 213 Po, a progeny of 225 Ac, improved from 9.41% to 4.98%. These findings are expected to contribute to more accurate isotope discrimination in alpha-particle imaging such as peak analysis and energy spectrum deconvolution.